1. Field of the Invention
Embodiments of the present invention generally relate to an apparatus and method of pretreatment of substrates before electroless deposition thereover. More specifically, embodiments of the present invention relate to an apparatus and method of annealing substrates in a thermal anneal chamber and/or a plasma anneal chamber before electroless deposition thereover.
2. Description of the Related Art
Reliably producing sub-micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large scale integration (ULSI) of semiconductor devices. However, as the fringes of circuit technology are pressed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on the processing capabilities. The multilevel interconnects that lie at the heart of this technology require precise processing of high aspect ratio features, such as vias and other interconnects. Reliable formation of these interconnects is very important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates.
As circuit densities increase, the widths of vias, contacts and other features, as well as the dielectric materials between them, decrease to sub-micron dimensions, whereas the thickness of the dielectric layers remains substantially constant, with the result that the aspect ratios for the features, i.e., their height divided by width, increases. Many traditional deposition processes have difficulty filling sub-micron structures where the aspect ratio exceeds 2:1, and particularly where the aspect ratio exceeds 4:1. Therefore, there is a great amount of ongoing effort being directed at the formation of substantially void-free, sub-micron features having high aspect ratios.
Electroless deposition has emerged as a promising process for depositing metal layers, such as for depositing capping layers, for depositing seed layers, for filling of sub-quarter micron sized high aspect ratio interconnect features, and for forming other metal layers. Electroless deposition involves an autocatalyzed chemical deposition process that does not require an applied current for the reaction to occur. Electroless deposition typically involves exposing a substrate to a solution by immersing the substrate in a bath or by spraying the solution over the substrate.
However, prior electroless deposition processing apparatuses and methods have faced substantial challenges in accurately controlling the electroless deposition process and the defect ratios in the resulting deposition layers. Thus, there is a need for improved electroless deposition apparatuses and methods capable of depositing controlled uniform layers having minimal defects.